1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are laminated is widely used.
The recording head is, for example, constructed so as to include a top pole and a bottom pole sandwiching a write gap, and a coil for generating a magnetic flux disposed between the top pole and the bottom pole with an insulating layer in-between. The top pole and the bottom pole have uniform widths which are the same as each other in the vicinity of the write gap in a region on a side close to a recording-medium-facing surface (air bearing surface) facing a magnetic recording medium (hereinbelow, simply referred to as “recording medium”). These parts constitute a “pole portion” for defining a recording track width.
In order to increase the recording density in performance of the recording head, it is necessary to make a width (pole width) of the pole portion extremely minute to the order of submicrons so as to increase the track density on the recording medium. In such a case, it is preferable to set the pole width uniform with high precision throughout the entire region of the pole portion. This is because a side-erasing phenomenon occurs when the pole width is partially wide. In the side-erasing phenomenon, a write operation is performed not only on a track region targeted for writing but also on its neighboring track region, so that information written upon the neighboring track region is overwritten and erased.
However, there is a problem that yield (rate of conforming item) is not sufficient at the time of manufacturing the thin film magnetic head because it is conventionally difficult to make the pole width uniform with high precision for the following reason. More specifically, at the time of forming the pole portion, for example, after the top pole is formed on the laminate of the bottom pole and the write gap so as to include a portion (uniform width portion) having an extremely minute uniform width corresponding to the recording track width, a region other than the portion corresponding to the uniform width portion in each of the bottom pole and the write gap is selectively etched and removed with the uniform width portion as a mask. Because ion milling is conventionally used as an etching method on the bottom pole and the write gap, an etching process is not performed uniformly when a difference is made in an irradiation amount of ion beam on the etching region owing to the structure of the top pole and the like, so that the width of the pole portion is increased in a region where the irradiation amount of ion beam is reduced. Such a problem is not resolved even though the etching process is performed while adjusting an irradiation angle of ion beam and/or rotating a substrate on which the pole portion and the like are formed.